Optical linked sensor network

ABSTRACT

Examples of an apparatus are disclosed. In some examples, an apparatus may comprise a first waveguide configured to propagate light originated from a light source, a first modulator coupled with the first waveguide, and a first sensor coupled with the first modulator. The apparatus may further comprise a second waveguide coupled with the first waveguide to form a propagation path for the light between the light source and a receiver device, a second modulator coupled with the second waveguide, and a second sensor coupled with the second modulator. The first modulator is configured to modulate the light propagating in the first waveguide based on sensor data from the first sensor, and the second modulator is configured to modulate the light propagating in the second waveguide based on sensor data from the second sensor, to enable the receiver device to obtain the sensor data.

BACKGROUND

The disclosure relates generally to sensor network, and morespecifically to optical linked sensor network in a wearable electronicdevice such as a head mounted display (HMD).

A wearable electronic device may include numerous sensors to supportdifferent applications of the device. For example, wearablevirtual-reality (VR) systems, augmented-reality (AR) systems, and mixedreality (MR) systems may include numerous image sensors. The imagesensors can be used to generate physical image data of a physicalenvironment in which a user is located. The physical image data can beprovided to a processor operating a simultaneous localization andmapping (SLAM) algorithm to track, for example, a location of the user,an orientation of the HMD, and/or a path of movement of the user in thephysical environment. The image sensors can also be used to generatephysical image data including stereo depth information for measuring adistance between the user and an object in the physical environment. Theimage sensors can also be configured as a near-infrared (NIR) sensor. Anilluminator may project a pattern of NIR light into the eyeballs of theuser. The internal structures of the eyeballs (e.g., the pupils) maygenerate a reflective pattern from the NIR light. The image sensors cancapture images of the reflective pattern, and provide the images to theprocessor to track the movement of the eyeballs of the user to determinea gaze point of the user. Based on these physical image data, theprocessor may determine a location and/or a movement of the user, arelative location of the user with respect to an object, a gazingdirection of the user, etc. Based on this information, the VR/AR/MRsystem can generate and update, for example, virtual image data fordisplaying to the user via the near-eye display, audio data foroutputting to the user via a speaker, etc., to provide an interactiveexperience to the user.

The industry has adopted various serial interface standards, such as thespecifications provided by Mobile Industry Processor Interface (MIPI),for data transmission between devices. For example, MIPI specificationdefines a set of standardized interfaces (e.g., Camera Serial Interface(CSI)) for connecting between devices (e.g., between an imaging deviceand a processing device). The specification defines a set of physicallayers including, for example, M-PHY, D-PHY, and C-PHY, for providingphysical connection between the imaging device and a processing device(e.g., an application processor) for transmission of data, as well as aset of protocol layers for processing of the data (e.g., pixel-byteconversion, error detection and correction, etc.). The standardizedphysical layers (e.g., M-PHY, D-PHY, and C-PHY) are typicallyimplemented as point-to-point interconnects. To provide connectionsbetween multiple imaging devices to a processing device, each imagingdevice may have a dedicated interconnect with the processing device.Each dedicated interconnect may include one or more data lanes fortransmitting sensor data. The data lanes are typically metal wires ortraces to transmit electrical signals representing the sensor data.

Although MIPI interfaces provide good performance, implementing thepoint-to-point MIPI physical layers for a sensor network comprisingmultiple sensors may be challenging, especially for a sensor network ina wearable device. To provide a dedicated interconnect between each ofthe sensors and a processor, a large number of electrical wires as wellas input-output (I/O) interface circuitries may be needed. Theelectrical wires can take up substantial space at least because each ofthese electrical wires needs to be shielded, or otherwise be spacedapart by a certain distance, to mitigate crosstalk between the wires asthey are carrying high speed signals typically at 1 GHz or above.Moreover, large signal power may be needed to overcome the resistanceand capacitance of the electrical wires, which increases the powerconsumption by the I/O interface circuitries. The space and power takenup by the interconnects further increase when multiple data lanes areincluded for each dedicated interconnect. Given that a wearable devicetypically has a small form factor and provides very limited space forelectrical wires and I/O interface circuitries, and that the wearabledevice needs to operate with low power, it becomes very challenging toMIPI physical layers for a sensor network in a wearable device.

Accordingly, there is a need for a sensor network which supports highspeed transmission of sensor data from multiple sensors, and whichoccupies a small area and consumes low power.

SUMMARY

The present disclosure relates to sensor network. More specifically, andwithout limitation, this disclosure relates to an optical sensor networkthat can be used in a wearable electronic device such as a head mounteddisplay (HMD).

In some examples, an apparatus is provided. The apparatus may comprise afirst waveguide configured to propagate light originated from a lightsource, a first modulator coupled with the first waveguide, and a firstsensor coupled with the first modulator. The apparatus may furthercomprise a second waveguide coupled with the first waveguide to form apropagation path for the light between the light source and a receiverdevice, a second modulator coupled with the second waveguide, and asecond sensor coupled with the second modulator. The first sensor isconfigured to generate first sensor data, and the first modulator isconfigured to modulate the light propagating in the first waveguidebased on the first sensor data. The second sensor is configured togenerate second sensor data, and the second modulator is configured tomodulate the light propagating in the second waveguide based on thesecond sensor data. The second waveguide is configured to propagate thelight modulated by at least one of the first modulator or the secondmodulator towards the receiver device, to enable the receiver device toobtain at least one of the first sensor data or the second sensor data.

In some aspects, the apparatus is a first apparatus that is part of awearable device. The light source and the receiver device are in asecond apparatus that is also part of the wearable device. At least oneof the first sensor or the second sensor comprises an image sensor.

In some aspects, the first modulator and the second modulator arescheduled to modulate the light transmitted in the first waveguide atdifferent times based on a time-division multiple access (TDMA) scheme.The light being modulated may be associated with a single wavelength.

In some aspects, the apparatus may further comprise a first buffercoupled with the first sensor and a second buffer coupled with thesecond sensor. The first buffer is configured to store the first sensordata generated by the first sensor during a time when the firstmodulator is not scheduled to modulate the light propagating in thefirst waveguide. The second buffer is configured to store the secondsensor data generated by the second sensor during a time when the secondmodulator is not scheduled to modulate the light propagating in thesecond waveguide.

In some aspects, the light being modulated may include a first componentassociated with a first wavelength and a second component associatedwith a second wavelength. The first modulator and the second modulatorare configured to modulate, respectively, the first component based onthe first sensor data and the second component based on the secondsensor data according to a wavelength division multiple access (WDMA)scheme.

In some aspects, the first modulator and the second modulator areconfigured to modulate, respectively, the first component and the secondcomponent at substantially identical time.

In some aspects, the first modulator is configured to modulate anintensity of the light propagating in the first waveguide, and thesecond modulator is configured to modulate an intensity of lightpropagating in the second waveguide.

In some aspects, the first modulator comprises a first ring resonator,the first ring resonator being associated with a configurable firstresonant frequency. The first ring resonator can change the intensity ofthe light propagating in the first waveguide based on a relationshipbetween the configurable first resonant frequency and a frequency of acomponent of the light propagating in the first waveguide. The secondmodulator comprises a second ring resonator, the second ring resonatorbeing associated with a configurable second resonant frequency. Thesecond ring resonator can change the intensity of the light propagatingin the second waveguide based on a relationship between the configurablesecond resonant frequency and a frequency of a component of the lightpropagating in the second waveguide. The first modulator is configuredto modulate the first resonant frequency of the first ring resonator tomodulate the intensity of the light propagating in the first waveguide.The second modulator is configured to modulate the second resonantfrequency of the second ring resonator to modulate the intensity of thelight propagating in the second waveguide.

In some aspects, the first modulator includes a first diode controllableto change the first resonant frequency of the first ring resonator by atleast changing a free carrier concentration within the first ringresonator. The second modulator includes a second diode controllable tochange the second resonant frequency of the second ring resonator by atleast changing a free carrier concentration within the second ringresonator.

In some aspects, the first waveguide comprises a first siliconwaveguide, and the second waveguide comprises a second siliconwaveguide.

In some aspects, the first silicon waveguide is part of a first chip.The second silicon waveguide is part of a second chip. The first siliconwaveguide of the first chip is coupled with the second silicon waveguideof the second chip via an optical fiber.

In some aspects, the apparatus further comprises a first grating couplerand a second grating coupler. The first grating coupler is coupled withthe first silicon waveguide and with a first end of the optical fiber todirect the light from the first silicon waveguide into the opticalfiber. The second grating coupler is coupled with a second end of theoptical fiber and with the second silicon waveguide to direct the lightfrom the optical fiber into the second silicon waveguide.

In some aspects, the first silicon waveguide and the first modulatorforms a first silicon photonic die. The first sensor is part of a firstsensor die. The first chip comprises the first sensor die and the firstsilicon photonic die forming a first vertical stack structure. Thesecond silicon waveguide and the second modulator forms a second siliconphotonic die. The second sensor is part of a second sensor die. Thesecond chip comprises the second sensor die and the second siliconphotonic die forming a second vertical stack structure.

In some aspects, the first sensor data and the second sensor data aredefined according to an application layer protocol specification ofMobile Industry Processor Interface (MIPI).

In some aspects, the apparatus further comprises a set of electricalsignal paths coupled with each of the first sensor and the secondsensor. The set of electrical signal paths are configured to transmitcontrol signals and clock signals from a controller to each of the firstsensor and to the second sensor.

In some aspects, the first waveguide and the second waveguide forms ashared physical medium over which one or more communication channels areformed, the physical medium being shared between the first sensor andthe second sensor for transmission of sensor data to the receiver deviceusing the one or more communication channels.

In some examples, a semiconductor chip is provided. The semiconductorchip includes a first semiconductor layer and a second semiconductorlayer. The first semiconductor layer includes one or more sensor devicesand one or more transistor devices configured to generate electricalsignals representing sensor data generated by the one or more sensordevices. The second semiconductor layer includes a waveguide and one ormore optical modulators configured to modulate light propagating in thewaveguide based on the electrical signals. The first semiconductor layerforms a stack structure with the second semiconductor layer along anaxis. The waveguide can be part of an optical link configured topropagate the light modulated based on the sensor data from a lightsource to a receiver system.

In some aspects, the one or more sensor devices comprise a photodiode.The one or more transistor devices are configured to generate theelectrical signals to represent an intensity of light received at thephotodiode.

In some aspects, the one or more sensor devices comprise amicroelectromechanical system configured to generate the sensor datarelated to a movement of one or more components of themicroelectromechanical system.

In some aspects, the one or more transistor devices include transistordevices that implement an analog-to-digital converter (ADC) configuredto generate a set of digital codes representing of the sensor data. Thedigital codes are transmitted via the electrical signals.

In some aspects, the one or more transistor devices are configured tooutput analog signals of the sensor data. The analog signals aretransmitted via the electrical signals. The second semiconductor furthercomprises an ADC configured to generate a set of digital codesrepresenting the analog signals and provide the set of digital codes tothe one or more optical modulators.

In some aspects, the one or more transistor devices include transistordevices that implement a buffer to store the sensor data generated bythe one or more sensor devices within a duration when the one or moreoptical modulators are not modulating the light propagating in thewaveguide.

In some aspects, the one or more optical modulators comprises a ringmodulator associated with a resonant frequency. The ring modulator isconfigured to modulate an intensity of a component of the light based ona relationship between a frequency of the component and the resonantfrequency.

In some aspects, the ring modulator is configured to modulate theintensity of the component of the light sequentially based on a set ofdigital codes representing the sensor data.

In some aspects, the ring modulator is optically coupled with thewaveguide at a coupling region within the second semiconductor layer.The ring modulator is configured to receive the light from the waveguidevia optical coupling when the light enters the coupling region, and tocause a phase shift in the light that re-enters the coupling regionafter propagating around the ring modulator to modulate the intensity ofthe light that exits from the coupling region and enters the waveguide.

In some aspects, a magnitude of the phase shift of the light is relatedto at least one of: a refractive index of the ring modulator, acircumference of the ring resonator, or a temperature at the ringmodulator when the light propagates around the ring modulator.

In some aspects, the ring modulator includes a P-N diode configured tomodulate the refractive index of the ring modulator based on theelectrical signals.

In some aspects, the one or more optical modulators comprises a singlemodulator configured to modulate a single component of the light, asingle component having a single frequency.

In some aspects, the one or more optical modulators comprises multiplemodulators configured to modulate multiple components of the light, themultiple components having multiple frequencies.

In some aspects, the second semiconductor layer further includes a firstgrating coupler and a second grating coupler each coupled with an end ofthe waveguide. The first grating coupler is configured to direct thelight into the waveguide. The second grating coupler is configured todirect the light out of the waveguide.

In some aspects, the semiconductor chip further includes one or moreinterconnects between the first semiconductor layer and the secondsemiconductor layer. The one or more interconnects comprise at least oneof: a through-silicon-via (TSV), a micro bump interconnection, awire-bound, or a controlled collapse chip connection.

In some examples, a method is provided. The method comprisestransmitting light through a propagation path comprising a firstwaveguide and a second waveguide, the light being originated at a lightsource; modulating the light transmitted in the first waveguide based onfirst sensor data generated by a first sensor; modulating the lighttransmitted in the second waveguide based on second sensor datagenerated by a second sensor; and transmitting, via the secondwaveguide, the light modulated based on at least one of the first sensordata or the second sensor data towards a receiver device.

In some aspects, modulating the light transmitted in the first waveguidecomprises modulating a first frequency component of the lighttransmitted in the first waveguide. Modulating the light transmitted inthe second waveguide comprises modulating the first frequency componentof the light transmitted in the second waveguide.

In some aspects, modulating the light in the first waveguide comprisesmodulating a first frequency component of the light transmitted in thefirst waveguide. Modulating the light transmitted in the secondwaveguide comprises modulating a second frequency component of the lighttransmitted in the second waveguide.

BRIEF DESCRIPTION OF THE DRAWINGS

Illustrative embodiments are described with reference to the followingfigures:

FIGS. 1A and 1B are diagrams of an example of a near-eye display.

FIG. 2 is an example of a cross section of the near-eye display.

FIG. 3 illustrates an isometric view of an example of a waveguidedisplay with a single source assembly.

FIG. 4 illustrates a cross section of an example of the waveguidedisplay.

FIGS. 5A, 5B, 5C, and 5D are block diagrams of an example of a systemincluding the near-eye display.

FIG. 6 is a block diagram of an example of an optical linked sensornetwork that can be used in the example system of FIG. 5A.

FIG. 7 is a block diagram illustrating a time-division multiple access(TDMA) scheme operable on the optical linked sensor network of FIG. 6.

FIG. 8 is a block diagram illustrating a wavelength-division multipleaccess (WDMA) scheme operable on the optical linked sensor network ofFIG. 6.

FIG. 9 is a side-view of an example of a component of the optical linkedsensor network of FIG. 6.

FIGS. 10A, 10B, 10C, and 10D are examples of operation of an opticalmodulator that can be used in the optical linked sensor network of FIG.6.

FIG. 11 is flowchart illustrating an example process of operating anoptical linked sensor network.

The figures depict embodiments of the present disclosure for purposes ofillustration only. One skilled in the art will readily recognize fromthe following description that alternative embodiments of the structuresand methods illustrated may be employed without departing from theprinciples, or benefits touted, of this disclosure.

In the appended figures, similar components and/or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If only the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

DETAILED DESCRIPTION

In the following description, for the purposes of explanation, specificdetails are set forth in order to provide a thorough understanding ofcertain inventive embodiments. However, it will be apparent that variousembodiments may be practiced without these specific details. The figuresand description are not intended to be restrictive.

This disclosure relates to an optical linked sensor network. The sensornetwork may include an optical link configured to transmit light from alight source to a receiver device. The optical link includes a firstwaveguide and a second waveguide. The sensor network may include a firstsensor coupled with the first waveguide via a first modulator, and asecond sensor coupled with the second waveguide via a second modulator.The first sensor may generate first sensor data, and use the firstmodulator to modulate the light based on the first sensor data when thelight travels in the first waveguide. The second sensor may generatesecond sensor data, and use the second modulator to modulate the lightbased on the second sensor data when the light travels in the secondwaveguide. The light being modulated by at least one of the firstmodulator or the second modulator can be received at the receiverdevice, which can obtain at least one of the first sensor data and thesecond sensor data from the modulated light.

The disclosed techniques provide high speed data transmission frommultiple sensors to a receiving device (e.g., a processor) using anoptical link that can be shared between the multiple sensors. Comparedwith point-to-point interconnects, the disclosed techniques cansubstantially reduce the number of interconnects between the sensors andthe receiving device. With fewer interconnects and the associated I/Ointerface circuitries, the space and power required for the sensornetwork can be reduced. On the other hand, compared with an electricalwire, an optical link provides a medium that supports a higher datatransmission rate and requires much lower power to transmit data at agiven data transmission rate. All these can facilitate the integrationof multiple sensors in a wearable device, as well as the high speedtransmission and processing of large volume of sensor data from themultiple sensors, to improve user experience.

Embodiments of the disclosure may include or be implemented inconjunction with an artificial reality system. Artificial reality is aform of reality that has been adjusted in some manner beforepresentation to a user, which may include, e.g., a virtual reality (VR),an augmented reality (AR), a mixed reality (MR), a hybrid reality, orsome combination and/or derivatives thereof. Artificial reality contentmay include completely generated content or generated content combinedwith captured (e.g., real-world) content. The artificial reality contentmay include video, audio, haptic feedback, or some combination thereof,any of which may be presented in a single channel or in multiplechannels (such as stereo video that produces a three-dimensional effectto the viewer). Additionally, in some embodiments, artificial realitymay also be associated with applications, products, accessories,services, or some combination thereof, that are used to, e.g., createcontent in an artificial reality and/or are otherwise used in (e.g.,perform activities in) an artificial reality. The artificial realitysystem that provides the artificial reality content may be implementedon various platforms, including a head-mounted display (HMD) connectedto a host computer system, a standalone HMD, a mobile device orcomputing system, or any other hardware platform capable of providingartificial reality content to one or more viewers.

FIG. 1A is a diagram of an embodiment of a near-eye display 100.Near-eye display 100 presents media to a user. Examples of mediapresented by near-eye display 100 include one or more images, video,and/or audio. In some embodiments, audio is presented via an externaldevice (e.g., speakers and/or headphones) that receives audioinformation from the near-eye display 100, a console, or both, andpresents audio data based on the audio information. Near-eye display 100is generally configured to operate as a virtual reality (VR) display. Insome embodiments, near-eye display 100 is modified to operate as anaugmented reality (AR) display and/or a mixed reality (MR) display.

Near-eye display 100 includes a frame 105 and a display 110. Frame 105is coupled to one or more optical elements. Display 110 is configuredfor the user to see content presented by near-eye display 100. In someembodiments, display 110 comprises a waveguide display assembly fordirecting light from one or more images to an eye of the user.

Near-eye display 100 further includes image sensors 120 a, 120 b, 120 c,and 120 d. Each of image sensors 120 a, 120 b, 120 c, and 120 d mayinclude a pixel array configured to generate image data representingdifferent fields of views along different directions. For example,sensors 120 a and 120 b may be configured to provide image datarepresenting two field of views towards a direction A along the Z axis,whereas sensor 120 c may be configured to provide image datarepresenting a field of view towards a direction B along the X axis, andsensor 120 d may be configured to provide image data representing afield of view towards a direction C along the X axis.

In some embodiments, sensors 120 a-120 d can be configured as inputdevices to control or influence the display content of the near-eyedisplay 100, to provide an interactive VR/AR/MR experience to a user whowears near-eye display 100. For example, sensors 120 a-120 d cangenerate physical image data of a physical environment in which the useris located. The physical image data can be provided to a locationtracking system to track a location and/or a path of movement of theuser in the physical environment. A system can then update the imagedata provided to display 110 based on, for example, the location andorientation of the user, to provide the interactive experience. In someembodiments, the location tracking system may operate a SLAM algorithmto track a set of objects in the physical environment and within a viewof field of the user as the user moves within the physical environment.The location tracking system can construct and update a map of thephysical environment based on the set of objects, and track the locationof the user within the map. By providing image data corresponding tomultiple fields of views, sensors 120 a-120 d can provide the locationtracking system a more holistic view of the physical environment, whichcan lead to more objects to be included in the construction and updatingof the map. With such arrangement, the accuracy and robustness oftracking a location of the user within the physical environment can beimproved.

In some embodiments, near-eye display 100 may further include one ormore active illuminator 130 to project light into the physicalenvironment. The light projected can be associated with differentfrequency spectrums (e.g., visible light, infra-red light, ultra-violetlight, etc.), and can serve various purposes. For example, illuminator130 may project light in a dark environment (or in an environment withlow intensity of infra-red light, ultra-violet light, etc.) to assistsensors 120 a-120 d in capturing images of different objects within thedark environment to, for example, enable location tracking of the user.Illuminator 130 may project certain markers onto the objects within theenvironment, to assist the location tracking system in identifying theobjects for map construction/updating.

In some embodiments, illuminator 130 may also enable stereoscopicimaging. For example, one or more of sensors 120 a or 120 b can includeboth a first pixel array for visible light sensing and a second pixelarray for infra-red (IR) light sensing. The first pixel array can beoverlaid with a color filter (e.g., a Bayer filter), with each pixel ofthe first pixel array being configured to measure intensity of lightassociated with a particular color (e.g., one of red, green or bluecolors). The second pixel array (for IR light sensing) can also beoverlaid with a filter that allows only IR light through, with eachpixel of the second pixel array being configured to measure intensity ofIR lights. The pixel arrays can generate an RGB image and an IR image ofan object, with each pixel of the IR image being mapped to each pixel ofthe RGB image. Illuminator 130 may project a set of IR markers on theobject, the images of which can be captured by the IR pixel array. Basedon a distribution of the IR markers of the object as shown in the image,the system can estimate a distance of different parts of the object fromthe IR pixel array, and generate a stereoscopic image of the objectbased on the distances. Based on the stereoscopic image of the object,the system can determine, for example, a relative position of the objectwith respect to the user, and can update the image data provided todisplay 100 based on the relative position information to provide theinteractive experience.

As discussed above, near-eye display 100 may be operated in environmentsassociated with a very wide range of light intensities. For example,near-eye display 100 may be operated in an indoor environment or in anoutdoor environment, and/or at different times of the day. Near-eyedisplay 100 may also operate with or without active illuminator 130being turned on. As a result, image sensors 120 a-120 d may need to havea wide dynamic range to be able to operate properly (e.g., to generatean output that correlates with the intensity of incident light) across avery wide range of light intensities associated with different operatingenvironments for near-eye display 100.

FIG. 1B is a diagram of another embodiment of near-eye display 100. FIG.1B illustrates a side of near-eye display 100 that faces the eyeball(s)135 of the user who wears near-eye display 100. As shown in FIG. 1B,near-eye display 100 may further include a plurality of illuminators 140a, 140 b, 140 c, 140 d, 140 e, and 140 f. Near-eye display 100 furtherincludes a plurality of image sensors 150 a and 150 b. Illuminators 140a, 140 b, and 140 c may emit lights of certain frequency range (e.g.,NIR) towards direction D (which is opposite to direction A of FIG. 1A).The emitted light may be associated with a certain pattern, and can bereflected by the left eyeball of the user. Sensor 150 a may include apixel array to receive the reflected light and generate an image of thereflected pattern. Similarly, illuminators 140 d, 140 e, and 140 f mayemit NIR lights carrying the pattern. The NIR lights can be reflected bythe right eyeball of the user, and may be received by sensor 150 b.Sensor 150 b may also include a pixel array to generate an image of thereflected pattern. Based on the images of the reflected pattern fromsensors 150 a and 150 b, the system can determine a gaze point of theuser, and update the image data provided to display 100 based on thedetermined gaze point to provide an interactive experience to the user.

As discussed above, to avoid damaging the eyeballs of the user,illuminators 140 a, 140 b, 140 c, 140 d, 140 e, and 140 f are typicallyconfigured to output lights of very low intensities. In a case whereimage sensors 150 a and 150 b comprise the same sensor devices as imagesensors 120 a-120 d of FIG. 1A, the image sensors 120 a-120 d may needto be able to generate an output that correlates with the intensity ofincident light when the intensity of the incident light is very low,which may further increase the dynamic range requirement of the imagesensors.

Moreover, the image sensors 120 a-120 d may need to be able to generatean output at a high speed to track the movements of the eyeballs. Forexample, a user's eyeball can perform a very rapid movement (e.g., asaccade movement) in which there can be a quick jump from one eyeballposition to another. To track the rapid movement of the user's eyeball,image sensors 120 a-120 d need to generate images of the eyeball at highspeed. For example, the rate at which the image sensors generate animage frame (the frame rate) needs to at least match the speed ofmovement of the eyeball. The high frame rate requires short totalexposure time for all of the pixel cells involved in generating theimage frame, as well as high speed for converting the sensor outputsinto digital values for image generation. Moreover, as discussed above,the image sensors also need to be able to operate at an environment withlow light intensity.

FIG. 2 is an embodiment of a cross section 200 of near-eye display 100illustrated in FIG. 1. Display 110 includes at least one waveguidedisplay assembly 210. An exit pupil 230 is a location where a singleeyeball 220 of the user is positioned in an eyebox region when the userwears the near-eye display 100. For purposes of illustration, FIG. 2shows the cross section 200 associated eyeball 220 and a singlewaveguide display assembly 210, but a second waveguide display is usedfor a second eye of a user.

Waveguide display assembly 210 is configured to direct image light to aneyebox located at exit pupil 230 and to eyeball 220. Waveguide displayassembly 210 may be composed of one or more materials (e.g., plastic,glass, etc.) with one or more refractive indices. In some embodiments,near-eye display 100 includes one or more optical elements betweenwaveguide display assembly 210 and eyeball 220.

In some embodiments, waveguide display assembly 210 includes a stack ofone or more waveguide displays including, but not restricted to, astacked waveguide display, a varifocal waveguide display, etc. Thestacked waveguide display is a polychromatic display (e.g., ared-green-blue (RGB) display) created by stacking waveguide displayswhose respective monochromatic sources are of different colors. Thestacked waveguide display is also a polychromatic display that can beprojected on multiple planes (e.g., multi-planar colored display). Insome configurations, the stacked waveguide display is a monochromaticdisplay that can be projected on multiple planes (e.g., multi-planarmonochromatic display). The varifocal waveguide display is a displaythat can adjust a focal position of image light emitted from thewaveguide display. In alternate embodiments, waveguide display assembly210 may include the stacked waveguide display and the varifocalwaveguide display.

FIG. 3 illustrates an isometric view of an embodiment of a waveguidedisplay 300. In some embodiments, waveguide display 300 is a component(e.g., waveguide display assembly 210) of near-eye display 100. In someembodiments, waveguide display 300 is part of some other near-eyedisplay or other system that directs image light to a particularlocation.

Waveguide display 300 includes a source assembly 310, an outputwaveguide 320, and a controller 330. For purposes of illustration, FIG.3 shows the waveguide display 300 associated with a single eyeball 220,but in some embodiments, another waveguide display separate, orpartially separate, from the waveguide display 300 provides image lightto another eye of the user.

Source assembly 310 generates image light 355. Source assembly 310generates and outputs image light 355 to a coupling element 350 locatedon a first side 370-1 of output waveguide 320. Output waveguide 320 isan optical waveguide that outputs expanded image light 340 to an eyeball220 of a user. Output waveguide 320 receives image light 355 at one ormore coupling elements 350 located on the first side 370-1 and guidesreceived input image light 355 to a directing element 360. In someembodiments, coupling element 350 couples the image light 355 fromsource assembly 310 into output waveguide 320. Coupling element 350 maybe, e.g., a diffraction grating, a holographic grating, one or morecascaded reflectors, one or more prismatic surface elements, and/or anarray of holographic reflectors.

Directing element 360 redirects the received input image light 355 todecoupling element 365 such that the received input image light 355 isdecoupled out of output waveguide 320 via decoupling element 365.Directing element 360 is part of, or affixed to, first side 370-1 ofoutput waveguide 320. Decoupling element 365 is part of, or affixed to,second side 370-2 of output waveguide 320, such that directing element360 is opposed to the decoupling element 365. Directing element 360and/or decoupling element 365 may be, e.g., a diffraction grating, aholographic grating, one or more cascaded reflectors, one or moreprismatic surface elements, and/or an array of holographic reflectors.

Second side 370-2 represents a plane along an x-dimension and ay-dimension. Output waveguide 320 may be composed of one or morematerials that facilitate total internal reflection of image light 355.Output waveguide 320 may be composed of e.g., silicon, plastic, glass,and/or polymers. Output waveguide 320 has a relatively small formfactor. For example, output waveguide 320 may be approximately 50 mmwide along x-dimension, 30 mm long along y-dimension and 0.5-1 mm thickalong a z-dimension.

Controller 380 controls scanning operations of source assembly 310. Forexample, controller 380 can determine scanning instructions for thesource assembly 310. In some embodiments, the output waveguide 320outputs expanded image light 340 to the user's eyeball 220 with a largefield of view (FOV). For example, the expanded image light 340 isprovided to the user's eyeball 220 with a diagonal FOV (in x and y) of60 degrees and/or greater and/or 150 degrees and/or less. The outputwaveguide 320 is configured to provide an eyebox with a length of 20 mmor greater and/or equal to or less than 50 mm; and/or a width of 10 mmor greater and/or equal to or less than 50 mm.

Moreover, controller 380 also controls image light 355 generated bysource assembly 310 based on image data provided by, for example,sensors 120 a-120 d of FIG. 1A and sensors 150 a and 150 b of FIG. 1B.For example, image sensors 120 a-120 d may be located on first side370-1 to generate image data of a physical environment in front of theuser (e.g., for location determination). Moreover, image sensors 150 aand 150 b of FIG. 1B may be located on second side 370-2 to generateimage data of eyeball 220 (e.g., for gaze point determination) of theuser. Image sensors may interface with a remote console 390 that is notlocated within waveguide display 300. Sensors 120 a-120 d and 150 a-150b may provide image data to remote console 390 which may determine, forexample, a location of the user, a gaze point of the user, etc., anddetermine the content of the images to be displayed to the user. Remoteconsole 390 can transmit instructions to controller 380 related to thedetermined content. Based on the instructions, controller 380 cancontrol the generation and outputting of image light 355 by sourceassembly 310.

FIG. 4 illustrates an embodiment of a cross section 400 of the waveguidedisplay 300. The cross section 400 includes source assembly 310 andoutput waveguide 320. Source assembly 310 generates image light 355 inaccordance with instructions from the controller 330. Source assembly310 includes a source 410 and an optics system 415. Source 410 is alight source that generates coherent or partially coherent light. Source410 may be, e.g., a laser diode, a vertical cavity surface emittinglaser, and/or a light emitting diode. Optics system 415 includes one ormore optical components that condition the light from source 410.Conditioning light from source 410 may include, e.g., expanding,collimating, and/or adjusting orientation in accordance withinstructions from controller 330. The one or more optical components mayinclude one or more lenses, liquid lenses, mirrors, apertures, and/orgratings. In some embodiments, optics system 415 includes a liquid lenswith a plurality of electrodes that allows scanning of a beam of lightwith a threshold value of scanning angle to shift the beam of light to aregion outside the liquid lens. Light emitted from the optics system 415(and also source assembly 310) is referred to as image light 355.

Output waveguide 320 receives image light 355. Coupling element 350couples image light 355 from source assembly 310 into output waveguide320. In embodiments where coupling element 350 is diffraction grating, apitch of the diffraction grating is chosen such that total internalreflection occurs in output waveguide 320, and image light 355propagates internally in output waveguide 320 (e.g., by total internalreflection), toward decoupling element 365.

Directing element 360 redirects image light 355 toward decouplingelement 365 for decoupling from output waveguide 320. In embodimentswhere directing element 360 is a diffraction grating, the pitch of thediffraction grating is chosen to cause incident image light 355 to exitoutput waveguide 320 at angle(s) of inclination relative to a surface ofdecoupling element 365.

In some embodiments, directing element 360 and/or decoupling element 365are structurally similar. Expanded image light 340 exiting outputwaveguide 320 is expanded along one or more dimensions (e.g., may beelongated along x-dimension). In some embodiments, waveguide display 300includes a plurality of source assemblies 310 and a plurality of outputwaveguides 320. Each of source assemblies 310 emits a monochromaticimage light of a specific band of wavelength corresponding to a primarycolor (e.g., red, green, or blue). Each of output waveguides 320 may bestacked together with a distance of separation to output an expandedimage light 340 that is multi-colored.

FIG. 5A is a block diagram of an embodiment of a system 500 includingthe near-eye display 100. The system 500 comprises control circuitries510, an imaging device 535, and an input/output interface 540. Each ofimaging device 535 and input/output interface 540 is coupled to controlcircuitries 510. System 500 can be configured as a head-mounted device,a wearable device, etc.

Imaging device 535 includes near-eye display 100, which is a displaythat presents media to a user. Examples of media presented by thenear-eye display 100 include one or more images, video, and/or audio. Insome embodiments, audio is presented via an external device (e.g.,speakers and/or headphones) that receives audio information fromnear-eye display 100 and/or control circuitries 510 and presents audiodata based on the audio information to a user. In some embodiments,near-eye display 100 may also act as an AR eyewear glass. In someembodiments, near-eye display 100 augments views of a physical,real-world environment, with computer-generated elements (e.g., images,video, sound, etc.).

Near-eye display 100 includes waveguide display assembly 210, imagesensors 120 a-120 d and 150 a-150 b, one or more position sensors 525,and/or an inertial measurement unit (IMU) 530. Waveguide displayassembly 210 includes source assembly 310, output waveguide 320, andcontroller 380 as depicted in FIG. 3. IMU 530 is an electronic devicethat generates fast calibration data indicating an estimated position ofnear-eye display 100 relative to an initial position of near-eye display100 based on measurement signals received from one or more of positionsensors 525. The estimation of the position of near-eye display 100 canalso be based on or augmented by image data from image sensors 120 a-120d of FIG. 1A, which can generate image data of a physical environment inwhich the user (and near-eye display 100) is located. Further, imagesensors 150 a-150 b of FIG. 1B may generate image data for determining agaze point of the user, to identify an object of interest of the user.

The input/output interface 540 is a device that allows a user to sendaction requests to the control circuitries 510. An action request is arequest to perform a particular action. For example, an action requestmay be to start or end an application or to perform a particular actionwithin the application.

Control circuitries 510 provides media to near-eye display 100 forpresentation to the user in accordance with information received fromone or more of: imaging device 535, near-eye display 100, andinput/output interface 540. In some examples, control circuitries 510can be housed within system 500 configured as a head-mounted device. Insome examples, control circuitries 510 can be a standalone consoledevice communicatively coupled with other components of system 500. Inthe example shown in FIG. 5A, control circuitries 510 include anapplication store 545, a tracking module 550, and an engine 555.

Application store 545 stores one or more applications for execution bythe control circuitries 510. An application is a group of instructions,that, when executed by a processor, generates content for presentationto the user. Examples of applications include: gaming applications,conferencing applications, video playback application, or other suitableapplications.

Tracking module 550 calibrates system 500 using one or more calibrationparameters and may adjust one or more calibration parameters to reduceerror in determination of the position of the near-eye display 100.Moreover, tracking module 550 tracks movements of near-eye display 100using slow calibration information from the imaging device 535. Trackingmodule 550 also determines positions of a reference point of near-eyedisplay 100 using position information from the fast calibrationinformation.

Engine 555 executes applications within system 500 and receives positioninformation, acceleration information, velocity information, and/orpredicted future positions of near-eye display 100 from tracking module550. In some embodiments, information received by engine 555 may be usedfor producing a signal (e.g., display instructions) to waveguide displayassembly 210 that determines a type of content presented to the user.For example, to provide an interactive experience, engine 555 maydetermine the content to be presented to the user based on a location ofthe user (e.g., provided by tracking module 550), a gaze point of theuser (e.g., based on image data provided by imaging device 535), adistance between an object and user (e.g., based on image data providedby imaging device 535), etc.

In some examples, an optical link can be provided as part of system 500to facilitate high speed transmission of sensor data. The optical linkcan be shared among image sensors 120 a-120 d and 150 a-150 b, positionsensor(s) 525, and IMU 530 to form a sensor network. The sensor networkcan be coupled with control circuitries 510 to allow each sensor of thenetwork to transmit sensor data to control circuitries 510. By providingan optical link shared among the sensors instead of point-to-pointconnection for each sensor, the electrical wirings and the associatedI/O interface circuitries can be substantially reduced, which allows thesensor network to be more compact and requires much lower power tooperate, while providing a superior data transmission rate (comparedwith electrical wires). All these can facilitate the integration ofmultiple sensors in a wearable device, as well as the high speedtransmission and processing of large volume of sensor data from themultiple sensors, to improve user experience.

FIG. 5B and FIG. 5C illustrate an example of a MIPI C-PHY interface 560that can be used to support transmission of data from an image sensor(e.g., image sensor 120 a) to control circuitries 510 (e.g., to bereceived by engine 555 for processing). MIPI C-PHY interface 560 mayinclude a camera serial interface (CSI) transmitter 562 on the side ofimage sensor 120 a and a CSI receiver 564 on the side of controlcircuitries 510. An unidirectional high speed data link 565 can beformed between CSI transmitter 562 and CSI receiver 564 for transmissionof pixel data from image sensor 120 a to control circuitries 510. In theexample of FIG. 5B, high speed data link 565 can include multiple datalanes. In some other examples, high speed data link 565 can also includea single data lane. Referring to FIG. 5C, in a case where high speeddata link 565 comprises a single data lane, CSI transmitter 562 canreceive a stream of pixel data bytes from image sensor 120 a. A lanedistribution function (LDF) block can buffer the stream of pixel databytes, and transmit, using a transmitter circuit (labelled “SerDes”),the data bytes via the single data lane. In some examples, the databytes can be transmitted sequentially in groups of two bytes. On theother hand, in a case where high speed data link 565 includes N datalanes, the LDF block can distribute the data bytes among the multipledata lanes in a round-robin fashion. In the example of FIG. 5C, a firstgroup of two bytes (bytes 0 and 1) can be transmitted using data lane 1,a second group of two bytes (bytes 2 and 3) can be transmitted usingdata lane 2, and an N-th group of two bytes (bytes 2N−2 and 2N−1) can betransmitted using data lane N. In a case where interface 560 is an MIPID-PHY interface, groups of four bytes can be transmitted. Each data lanemay include multiple wires. In the example of FIG. 5B, each data lane ofhigh speed data link 565 may include three wires, and each data lane cansupport parallel transmission of three sets of data for transmission ofa pixel data byte stream. In some examples, a MIPI PHY interface (e.g.,MIPI D-PHY) may also include a clock lane (not shown in FIG. 5B) toprovide synchronization between a CSI transmitter and a CSI receiver. Insome examples, the MIPI PHY interface may include no dedicated clocklane, and the pixel data transmitted via the data lanes can be encodedbased on a self-clocking signal encoding scheme to includesynchronization information.

Moreover, MIPI C-PHY interface 560 also includes a camera controlinterface (CCI) including a CCI slave 566 on the side of image sensorand a CCI master 568 on the side of control circuitries 510. CCI enablescontrol circuitries 510 (e.g., engine 510) to configure and/or controlimage sensor 120 a (e.g., to update various configuration settings ofimage sensor 120 a, to control image sensor 120 a to transmit image dataat a certain time, etc.). A bidirectional control link 569 can be formedbetween CCI slave 566 and CCI master 568. Bidirectional control link 569may include a clock line (between SCL ports of CCI slave 566 and CCImaster 568) and one or more data lines (between SDA ports of CCI slave566 and CCI master 568). The bi-directional control link can beimplemented as Inter-Integrated Circuit (I²C) buses based on, forexample, the I2C and/or I3C standards.

In a case where multiple image sensors (e.g., image sensors 120 a-120 d)are connected with control circuitries 510 using MIPI C-PHY interface,multiple instances of MIPI C-PHY interface 560 can be included betweenthe multiple image sensors and control circuitries 510 to form apoint-to-point connection between control circuitries 510 and each imagesensor.

FIG. 5D illustrates an example of a CSI-2 system stack diagram. Thesystem stack diagram shows the processing components of a media controlaccess (MAC) layer 570 between an application (e.g., an application fromapplication store 545) and the PHY layer (e.g., MIPI C-PHY interface560) involved in the transmission and reception of pixel data on thetransmitter side and on the receiver side. On the transmitter side,pixel data generated by an application (e.g., based on sensor datagenerated by image sensor 120 a) can be packaged into data bytes basedon a pre-determined data format. The stream of data bytes can bebuffered at a lane management layer which includes the LDF of FIG. 5C todistribute the data bytes among multiple data lanes or to send the databytes via a single data lane. On the receiver side, the data bytes canbe collected and unpackaged to obtain the pixel data, which can then beprovided to another application (e.g., a SLAM algorithm) for furtherprocessing.

FIG. 6 illustrates an example of an optical linked sensor network 600,which can be used in lieu of the MIPI PHY layer (e.g., PHY layer of FIG.5D). In some examples, optical linked sensor network 600 can perform thedata transmission function of a MIPI PHY layer and is compatible withMAC layer 570 of FIG. 5D. Optical linked sensor network 600 can be partof system 500. Optical linked sensor network 600 includes a plurality ofsensors 602, 604, 606, and 608, an optical link 610 coupled between alight source 612 and a receiver system 614, and one or more electricalsignal paths 615. Sensors 602, 604, 606, and 608 can be, for example,image sensors 120 a-120 d and 150 a-150 b, position sensors 525, IMU530, etc. Both light source 612 and receiver system 614 can be coupledwith control circuitries 510. Light source 612 can be operated bycontrol circuitries 510 to generate light 616, which travels throughoptical link 610 to reach receiver system 614. Light 616 can bemodulated for transmission of data to control circuitries 510. AlthoughFIG. 6 illustrates a single optical link 610, it is understood thatmultiple optical links in addition to optical link 610 can be includedin system 500. For example, each additional optical link can representan additional data lane to further increase the rate of transmission ofsensor data to control circuitries 510. Moreover, as to be discussed inmore details below, a single optical link 610 can also be used toprovide the data transmission function of multiple data lanes.

Optical link 610 can be shared among the plurality of sensors 602, 604,606, and 608 for transmission of sensor data to control circuitries 510.As such, optical link 610 can provide a shared physical medium overwhich one or more communication channels can be provided to each ofsensors 602, 604, 606, and 608 to transmit data to control circuitries510. Each of sensors 602, 604, 606, and 608 may be coupled with opticallink 610 via, respectively, optical modulators 622, 624, 626, and 628.Each of optical modulators 622, 624, 626, and 628 may be associatedwith, respectively, sensors 602, 604, 606, and 608 to modulate light 616propagating at a certain location within optical link 610. Themodulation can be in different forms. In some examples, amplitudemodulation can be used to introduce an intensity pattern in light 616 totransmit the sensor data. In some examples, phase modulation can be usedto introduce a pattern of phase changes in light 616 to transmit thesensor data. In some examples, a combination of phase and amplitudemodulation schemes (e.g., quadrature phase-shift keying (QPSK),quadrature amplitude modulation (QAM), orthogonal frequency-divisionmultiplexing (QFDM), etc.) can be used to modulate light 616 to transmitthe sensor data. Receiver system 614 may include a photodetector (e.g.,a photodiode) and other circuitries (e.g., demodulators, oscillators,mixers, etc.) to convert the modulated light 616 to electrical signalsrepresenting the sensor data. The sensor data can then be provided tocontrol circuitries 510 for further processing (e.g., to track alocation of system 500, a direction of gaze of the user, etc.). In someexamples, each sensor can be configured to generate data packetsconforming to a MIPI protocol (e.g., Camera Serial Interface (CSI)),which enables control circuitries 510 to process the data packets basedon the MIPI protocol. With such arrangements, sensors and processingcircuitries that are interoperable according to the MIPI specificationcan be integrated easily using optical link 610 instead of a MIPIphysical layer which typically requires point-to-point connectionbetween each sensor and control circuitries 510 as discussed above.

There are different ways by which sensors 602, 604, 606, and 608 canshare optical link 610 to transmit sensor data to control circuitries510. In one example, sensors 602, 604, 606, and 608 can be configured toshare optical link 610 based on a time-division multiple access (TDMA)scheme. Reference is now made to FIG. 7, which illustrates an example ofa TDMA scheme. In the example of FIG. 7, each of optical modulators 622,624, 626, and 628 (and the associated sensors 602, 604, 606, and 608)can be assigned different time slots to modulate light 616 to transmitsensor data. For example, optical modulator 622 can be scheduled tomodulate light 616 at time T0. Optical modulator 624 can be scheduled tomodulate light 616 at time T1. Optical modulator 626 can be scheduled tomodulate light 616 at time T2. Optical modulator 628 can be scheduled tomodulate light 616 at time T3. The scheduling can be in a round-robinfashion. For example, after optical modulator 628 completes transmissionof sensor data at time T3, optical modulator 622 can be scheduled tomodulate light 616 at time T4, followed by modulator 624 at time T5,etc. Each of sensors 602, 604, 606, and 608 may be coupled with,respectively, buffers 702, 704, 706, and 708, to store sensor datagenerated by a sensor between the time slots when the sensor isscheduled to transmit sensor data (and when the associated opticalmodulator is scheduled to modulate light 616 based on the sensor data).For example, buffer 702 can be used to accumulate sensor data generatedby sensor 602 at times T1, T2, and T3. The accumulated sensor data atbuffer 702 can then transmitted at time T4, and buffer 702 can beemptied to store another set of sensor data generated subsequently.

In the example of FIG. 7, the TDMA scheme allows optical link 610 toperform the data transmission function of a four-lane MIPI D-PHY. Forexample, in a case the LDF of FIG. 5D is to distribute the data bytestream received from sensors 602, 604, 606, and 608 among four datalanes, the LDF may transmit four groups of bytes (e.g., each groupincludes two bytes for C-PHY) to be transmitted in four data lanes tooptical modulators 622, 624, 626, and 628. Each optical modulator canreceive a group of bytes and transmit the group of bytes in the timeslot allocated to the optical modulator. In the simplest case, atwo-lane MIPI D-PHY can be implemented in optical link 610 with a TDMAscheme where light 616 of a single wavelength can be modulatedalternately by the data of the first data lane and by the data of thesecond data lane. The data transmitted may also be encoded based on aself-clocking signal encoding scheme to include synchronizationinformation, such that a separate clock transmission is not required.

In some examples, as part of the TDMA scheme, some sensors can also beprioritized over others. For example, different sensors can be allocatedwith different durations of data transmission time and wait time basedon, for example, a volume of data to be transmitted, a criticality ofthe data, etc. For example, in a case where sensor 602 is an imagesensor and sensor 604 is a location sensor, and that sensor 602generates a larger volume of sensor data per unit time compared withsensor 604, the duration of time T0 allocated to sensor 602 can belonger than the duration of time T1 allocated to sensor 604. Moreover,the image data from sensor 602 may be deemed to be more time-sensitivethan the location data from sensor 604 (e.g., due to a higheracquisition rate) and are given a higher priority. As a result, sensor602 may be scheduled to transmit the image data before sensor 604transmits the location data, and sensor 602 may wait for a shorterduration than sensor 604 before transmitting the image data.

In some examples, the scheduling can be performed by control circuitries510, and the scheduling information can be communicated to each ofsensors 602, 604, 606, and 608 via electrical signal paths 615. In someexamples, control circuitries 510 can also assign an identifier to eachof sensors 602, 604, 606, and 608, each of which can include itsassigned identifier in the sensor data transmission. Control circuitries510 can then identify which sensor generates the received sensor databased on the time of receiving the sensor data, the identifierinformation included in the sensor data, or a combination of both. Forexample, each of the scheduled times T0, T1, T2, T4, etc., can berepresented by a set of reference count values. Control circuitries 510can associate the reference count values with each of sensors 602, 604,606, and 608, and transmit the counter values corresponding to times T0,T1, T2, T3, etc., to sensors 602, 604, 606, and 608. Each of controlcircuitries 510 and sensors 602, 605, 606, and 608 can also maintain afree-running counter clocked by a common clock signal generated bycontrol circuitries 510 and transmitted to each of the sensors. Eachsensor can initiate transmission of sensor data when the output of thefree-running counter at the sensor matches the stored reference countvalues, which indicates that the allocated time slot of transmission hasarrived. Moreover, control circuitries 510, upon receiving the sensordata from receiver device system 614, can determine the source of thesensor data by matching the output of the free-running counter atcontrol circuitries 510 with the stored reference count valuesassociated with the sensors, and/or based on the identifier informationincluded in the sensor data. Control circuitries 510 can performpre-determined processing of the sensor data based on the determinedsource. For example, if the sensor data are image data from sensors 120a-120 d, control circuitries 510 can process the sensor data forlocation tracking. Also, if the sensor data are image data from sensors150 a-150 b, control circuitries 510 can process the sensor data forgaze direction determination.

In the TDMA scheme of FIG. 7, each of optical modulators 622, 624, 626,and 628 may be configured to modulate a single frequency component oflight 616 associated with a particular range of wavelength, and eachmodulator (associated with a respective sensor) takes turn in modulatingthat single frequency component. In some examples to reduce the waittime and increase the rate of data transmission, sensors 602, 604, 606,and 608 can also be configured to share optical link 610 based on awavelength-division multiple access (WDMA) scheme, which allows eachsensor to use a dedicated frequency component of light 616 to transmitsensor data simultaneously, and the wait time can be reduced (orotherwise eliminated) for each sensor.

Reference is now made to FIG. 8, which illustrates an example of a WDMAscheme. In the example of FIG. 8, light source 612 may be configured togenerate light 616 including a plurality of frequency components, witheach frequency component being associated with a particularwavelength/frequency range. For example, as shown in FIG. 8, light 616may include a first frequency component 802 associated with wavelengthλ₁, a second frequency component 804 associated with wavelength λ₂, athird frequency component 806 associated with wavelength λ₃, and afourth frequency component 808 associated with wavelength λ₄. Each ofsensors 602, 604, 606, and 608 can be assigned to use one of the first,second, third, and fourth frequency components 602-608 for datatransmission. For example, based on the assignment, optical modulator622 may be configured to modulate first frequency component 802 based onsensor data generated by sensor 602, optical modulator 624 may beconfigured to modulate second frequency component 804 based on sensordata generated by sensor 604, optical modulator 626 may be configured tomodulate third frequency component 806 based on sensor data generated bysensor 606, whereas optical modulator 628 may be configured to modulatefourth frequency component 808.

The WDMA scheme can perform the data transmission function of amulti-lane MIPI PHY interface as well. For example, each frequencycomponent can correspond to one data lane. In a case the LDF of FIG. 5Dis to distribute the data byte stream received from sensors 602, 604,606, and 608 among four data lanes, the LDF may transmit four groups ofbytes (e.g., each group includes two bytes for C-PHY) to be transmittedin four data lanes to optical modulators 622, 624, 626, and 628. Eachoptical modulator can receive a group of bytes and transmit the group ofbytes using the assigned frequency component. The data transmitted mayalso be encoded based on a self-clocking signal encoding scheme toinclude synchronization information, such that a separate clocktransmission is not required.

On the receiver side, receiver system 614 may include a set of receivers812, 814, 816, and 818, with each receiver configured to process one ofthe first, second, third, and fourth frequency components 602-608. Forexample, receiver 812 may be configured to process first frequencycomponent 802 that carries sensor data from sensor 602, receiver 814 maybe configured to process second frequency component 804 that carriessensor data from sensor 604, receiver 816 may be configured to processthird frequency component 806 that carries sensor data from sensor 606,and receiver 818 may be configured to process fourth frequency component808 that carries sensor data from sensor 608. Each of receivers 812,814, 816, and 818 also includes a photodetector (e.g., a photodiode) toconvert the modulated frequency components to electrical signalsrepresenting the sensor data. The sensor data can then be provided tocontrol circuitries 510 for further processing (e.g., to track alocation of system 500, a direction of gaze of the user, etc.). Controlcircuitries 510 can maintain a mapping between the receivers and thesensors based on the frequency component assignment, and performdifferent pre-determined processing for sensor data provided bydifferent receivers (and originated from different sensors), asdiscussed above.

In some examples, the sensors of optical linked sensor network 600 canalso share optical link 610 based on a combination of the aforementionedTDMA and WDMA schemes. For example, to prioritize the data transmissionby certain sensors, each sensor with higher priority can be assigned adedicated frequency component of light 616 for data transmission basedon a WDMA scheme, whereas sensors with lower priority can be configuredto time-share a single frequency component of light 616 based on a TDMAscheme. As another example, optical linked sensor network 600 can switchbetween a WDMA scheme and a TDMA scheme based on a mode of operation.For example, under a low power mode, the image sensors can be configuredto generate images with lower resolution and at a lower frame rate. Inthis mode, optical link 610 can be operated under a TDMA scheme, whereeach image sensor takes turns in using a single frequency component oflight 616 to transmit the image data, based on the lower bandwidthrequirement. On the other hand, under a high power mode, the imagesensors can be configured to generate images with higher resolution andat a higher frame rate, and optical link 610 can be operated under aWDMA scheme, where each image sensor uses a dedicated frequencycomponent of light 616 to transmit the image data, based on the higherbandwidth requirement. The switching between lower power mode and highpower mode can be based on, for example, a state of motion of thewearable device (e.g., a HMD) that incorporates optical linked sensornetwork 600. As an example, if control circuitries 510 determines thatthe wearable device remains static for a pre-determined time duration,control circuitries 510 may configure sensors 602, 604, 606, and 608, aswell as receiver system 614, to operate based on a TDMA scheme. In sucha case, control circuitries 510 may configure the sensors to time-sharea single frequency component (e.g., first frequency component 802associated with wavelength λ₁) for data transmission, and enablereceiver 812 for receiving and processing that frequency component.Control circuitries 510 can also disable receivers 814, 816, and 818under the TDMA scheme.

Referring back to FIG. 6, optical linked sensor network 600 furtherincludes one or more electrical signal paths 615. Electrical signalpaths 615 can include buses used for transmission of control signals andclock signals from control circuitries 510 to each of sensors 602, 604,606, and 608. For example, control circuitries 510 can transmitscheduling information (e.g., reference counter values) to each sensorusing electrical signal paths 615. Control circuitries 510 can alsotransmit clock signals using electrical signal paths 615 to synchronizebetween the data transmission operation at each sensor and the datarecovery operation at receiver system 614. In some examples, electricalsignal paths may include Inter-Integrated Circuit (I²C) buses.

In some examples, optical link 610 may include a plurality of waveguidesto provide a propagation path for light 616 between light source 612 andreceiver system 614. Each waveguide may include a silicon waveguide,which can be integrated with, and associated with, a silicon opticalmodulator (e.g., one of optical modulators 622, 624, 626, or 628) on asilicon photonic die. Each silicon photonic die can include one or moresilicon waveguides and one or more optical modulators associated withthe one or more silicon waveguides. One or more sensor devices (e.g.,pixel arrays, microelectromechanical systems (MEMS), etc.) as well asinterfacing and processing circuitries can be coupled with a siliconphotonic die to form a single chip. In some examples, the sensor devicescan be integrated with the one or more silicon optical modulators andthe one or more silicon waveguides on the silicon photonic die to form asingle silicon chip. In some examples, the sensor devices can beintegrated on a sensor die. The sensor die and the silicon photonic diecan be coupled together to form a vertical stack. The vertical stack canbe housed within a chip package to form a single chip. A vertical stackmay be preferable for image sensors to maximize the available area forpixel array on the wearable device. By incorporating a larger pixelarray with more pixels, the resolution of images generated by the imagesensor can be increased.

Reference is now made to FIG. 9, which illustrates a cross-section viewof an example of a chip 900 that can be part of optically linked sensornetwork 600 of FIG. 6. Chip 900 includes a sensor die 902 and a siliconphotonic die 904. Sensor die 902 may include a semiconductor substrate908 (e.g., a silicon substrate, a silicon germanium substrate, etc.) inwhich one or more sensor devices 910 (e.g., pixel arrays,microelectromechanical systems (MEMS), etc.) as well as processing andinterfacing circuitries 912 may be formed. Sensor die 902 may form avertical stack structure with silicon photonic die 904. Interconnect 920can be provided to allow transmission of signals and power betweensensor die 902 and silicon photonic die 904. Interconnect 920 caninclude, for example, Through-silicon-via (TSV), micro bumpinterconnection, wire-bound, controlled collapse chip connection (C4),etc.

Silicon photonic die 904 may include a silicon layer 930, an uppercladding layer 932, a lower cladding layer 934, and a silicon substrate936. Silicon layer 930 can be configured as a silicon-on-insulator (SOI)layer to include a silicon waveguide for propagating light 616 along thex direction. Silicon layer 930 is sandwiched between upper claddinglayer 932 and lower cladding layer 934. The two cladding layers mayinclude, for example, silicon dioxide, or other materials with a lowerrefractive index than silicon layer 930. The cladding layers can beprovided to confine light 616 within silicon layer 930. In addition,silicon layer 930 may also include an optical modulator 940 adjacent tothe silicon waveguide (e.g., along the y direction). As to be discussedin more detail below, optical modulator 940 can be controlled by, forexample, processing and interfacing circuitries 912 of sensor die 902 tomodulate light 616 when light 616 propagates in the silicon waveguide ofsilicon layer 930.

In some examples, processing and interfacing circuitries 912 may includeanalog to digital converter (ADC) circuits configured to convert analogelectrical signals representing the sensor data generated by sensordevices 910 (e.g., a voltage and/or a current representing an intensityof light detected at a pixel cell, a voltage and/or a currentrepresenting a degree of movement of one or more components of the MEMS,etc.) into digital codes. The digital codes can be provided to opticalmodulator 940 in the form of electrical control signals. Opticalmodulator 940 can then modulate light 616 based on the electricalcontrol signals. For example, optical modulator 940 can modulate light616 sequentially (with respect to time) according to the digital codes.In some examples, the ADC circuits can also be in silicon photonic die904. In that case, sensor die 902 can transmit the analog electricalsignals representing the sensor data generated by sensor devices 910 tothe ADC in silicon photonic die 904. The ADC in silicon photonic die 904can convert the analog electrical signals to digital codes and providethe digital codes to optical modulator 940. In some examples, processingand interfacing circuitries 912 may include a buffer to store thedigital codes representing sensor data collected within a period of timewhen chip 900 is not scheduled to transmit the sensor data over theoptical link (e.g., in the TDMA scheme as described above).

The silicon waveguide of silicon layer 930 can be coupled with thesilicon waveguides of other chips to form optical link 610. The couplingcan be through fiber optics. As shown in FIG. 9, silicon photonic die904 may include a pair of grating couplers 950 and 952. Grating coupler950 can act as an interface between optical fiber 954 and the siliconwaveguide of silicon layer 930, whereas grating coupler 952 can act asan interface between the silicon waveguide and optical fiber 956. Bothgrating couplers can be configured to focus light 616 into apre-determined direction, to reduce the energy loss of light 616 due toscattering and diffraction as the light enters or exits the siliconwaveguide.

Reference is now made to FIG. 10A, which illustrates an overhead view ofchip 900 of FIG. 9. As shown in FIG. 10A, chip 900 includes gratingcouplers 950 and 952, a silicon waveguide 1002 (formed in silicon layer930), and a ring resonator 1004 which is configured as an opticalmodulator. Optical coupling can occur between silicon waveguide 1002 andring resonator 1004 when light 616 propagates through a coupling region1006 between silicon waveguide 1002 and ring resonator 1004. Withoptical coupling, light 616 entering coupling region 1006 will betransmitted into ring resonator 1004. Light 616 may propagate aroundring resonator 1004, and some of it may re-enter waveguide 1002 and exitchip 900. In a case where light 616 accumulates a phase shift of 2π aslight 616 re-enters coupling region 1006, critical coupling may occur,in which case light 616 will stay in ring resonator 1004 and will notre-enter silicon waveguide 1002. The phase shift experienced by light116 as it propagates in ring resonator 1004 may be a function of, forexample, the refractive index (n_(eff)) of ring resonator 1004, thefrequency (or wavelength) of light 616, the circumference of ringresonator 1004, the temperature, etc. For example, as shown in FIG. 10B,for a given temperature, circumference, and refractive index of ringresonator 1004, the resonant frequency is 206 Terahertz (1 THz=10¹² Hz).For a component of light 616 associated with the resonant frequency,critical coupling may occur, and a transmission ratio (e.g., between thepower of light 616 entering resonator 1004 and the power of light 616re-entering silicon waveguide 1002) can become zero. In such as case,the component of light 616 stays in ring resonator 1004 and does notre-enter silicon waveguide 1002.

Ring resonator 1004 can be used to modulate the intensity of light 616re-entering waveguide 1002 from ring resonator 1004. For example,referring to FIG. 10C, the resonant frequency may shift due to, forexample, changes in the refractive index of ring resonator 1004. Becauseof the shift in resonant frequency, the transmission ratio for acomponent of light 616 with a 206 Terahertz can change from zero toclose to unity. By modulating the resonant frequency of ring resonator1004, the transmission ratio of light 616 may change accordingly, and anintensity of light 616 exiting waveguide 1002 can be modulated as aresult. The refractive index of ring resonator 1004 can be modulated bymodulating the free carrier density of the region of silicon layer 930that forms ring resonator 1004.

There are different ways of modulating the free carrier density of ringresonator 1004. One way is by employing a P-N diode. Reference is nowmade to FIG. 10D, which illustrates an example of ring resonator 1004with a P-N diode. The P-N diode may include a region 1052 of siliconlayer 930 with P-type carriers, and a region 1054 of silicon layer 930with N-type carriers. Part of ring resonator 1004 can be sandwichedbetween regions 1052 and 1054. The P-N diode may receive a reverse biasvoltage (e.g., with N-type region 1054 being biased at a higher voltagethan N-type region 1052) from a voltage source 1060. The reverse biasvoltage can create an electric field (e.g., indicated by field lines1070) across ring resonator 1004. The electric field can create adepletion region within ring resonator 1004 by, for example, sweepingfree P-type carriers within ring resonator 1004 towards N-type region1054 and N-type carriers within ring resonator 1004 towards P-typeregion 1052. By modulating the free carrier density of ring resonator1004, the refractive index as well as the resonant frequency of ringresonator 1004 can be modulated as well.

The ring resonator and P-N diode topology of FIG. 10D can be used foroptical modulation as well as at receiver system 614. For example, thereverse bias voltage of the P-N diode can be configured to set theresonant frequency of ring resonator 1004 at the frequency of thecomponent of light 616 to be modulated. On the receiver side, ringresonator 1004 with the P-N diode biased at the same reverse biasvoltage as the optical modulator side can be used as part of a band-passfilter to band-pass only the modulated component of light 616. Themodulated component can be provided to a photodetector to generateelectrical signals representing the sensor data.

While FIG. 10A-FIG. 10D illustrate the use of a ring resonator as anoptical modulator used in optically linked sensor network 600, it isunderstood other types of optical modulator can be used, such asMach-Zehnder-Interferometers (MZI), vertical-cavity surface-emittinglasers (VCSEL), etc.

FIG. 11 illustrates an embodiment of a flowchart of a process 1100 foroperating an optical linked sensor network (e.g., optical linked sensornetwork 600 of FIG. 6). Process 1100 beings in step 1102, where lightoriginated at a light source is transmitted through a propagation pathcomprising a first waveguide and a second waveguide. The first waveguidecan include a silicon waveguide and can be coupled with a first sensorvia a first optical modulator. The second waveguide can also include asilicon waveguide and can be coupled with a second sensor via a secondoptical modulator. The first and second sensor may include, for example,image sensors configured to capture images of a physical environment forlocation tracking, images of a user's eyeballs for gaze directiondetermination, etc.

At step 1104, the light transmitted in the first waveguide can bemodulated by the first optical modulator based on first sensor datagenerated by the first sensor. At step 1106, the light transmitted inthe second waveguide can be modulated by the second optical modulatorbased on second sensor data generated by the second sensor. Themodulation of the light by the first optical modulator and by the secondmodulator can be based on a TDMA scheme, a WDMA scheme, or a combinationof both. For example, with TDMA, the first optical modulator and thesecond optical modulator can be scheduled to modulate the light atdifferent times. With WDMA, the first optical modulator and the secondoptical modulator can be configured to modulate different frequencycomponents of the light at substantially the same time. The modulationcan be in the form of amplitude modulation, phase modulation, or acombination of both.

At step 1108, the light modulated based on at least one of the firstsensor data or the second sensor data can be transmitted towards areceiver device via the second waveguide. The modulated light can beconverted to electrical signals by a photodetector at the receiverdevice. The electrical signals can be provided to a controller toextract the at least one of the first sensor data or the second sensordata, and to perform additional processing of the extracted data (e.g.,for location tracking, gaze direction determination, etc.).

The foregoing description of the embodiments of the disclosure has beenpresented for the purpose of illustration; it is not intended to beexhaustive or to limit the disclosure to the precise forms disclosed.Persons skilled in the relevant art can appreciate that manymodifications and variations are possible in light of the abovedisclosure.

Some portions of this description describe the embodiments of thedisclosure in terms of algorithms and symbolic representations ofoperations on information. These algorithmic descriptions andrepresentations are commonly used by those skilled in the dataprocessing arts to convey the substance of their work effectively toothers skilled in the art. These operations, while describedfunctionally, computationally, or logically, are understood to beimplemented by computer programs or equivalent electrical circuits,microcode, or the like. Furthermore, it has also proven convenient attimes, to refer to these arrangements of operations as modules, withoutloss of generality. The described operations and their associatedmodules may be embodied in software, firmware, and/or hardware.

Steps, operations, or processes described may be performed orimplemented with one or more hardware or software modules, alone or incombination with other devices. In some embodiments, a software moduleis implemented with a computer program product comprising acomputer-readable medium containing computer program code, which can beexecuted by a computer processor for performing any or all of the steps,operations, or processes described.

Embodiments of the disclosure may also relate to an apparatus forperforming the operations described. The apparatus may be speciallyconstructed for the required purposes, and/or it may comprise ageneral-purpose computing device selectively activated or reconfiguredby a computer program stored in the computer. Such a computer programmay be stored in a non-transitory, tangible computer readable storagemedium, or any type of media suitable for storing electronicinstructions, which may be coupled to a computer system bus.Furthermore, any computing systems referred to in the specification mayinclude a single processor or may be architectures employing multipleprocessor designs for increased computing capability.

Embodiments of the disclosure may also relate to a product that isproduced by a computing process described herein. Such a product maycomprise information resulting from a computing process, where theinformation is stored on a non-transitory, tangible computer readablestorage medium and may include any embodiment of a computer programproduct or other data combination described herein.

The language used in the specification has been principally selected forreadability and instructional purposes, and it may not have beenselected to delineate or circumscribe the inventive subject matter. Itis therefore intended that the scope of the disclosure be limited not bythis detailed description, but rather by any claims that issue on anapplication based hereon. Accordingly, the disclosure of the embodimentsis intended to be illustrative, but not limiting, of the scope of thedisclosure, which is set forth in the following claims.

The invention claimed is:
 1. An apparatus being part of a wearabledevice, the apparatus comprising: a first waveguide configured topropagate light originated from a light source; a first modulatorcoupled with the first waveguide; an image sensor coupled with the firstmodulator; a second waveguide coupled with the first waveguide to form apropagation path for the light between the light source and a receiverdevice; a second modulator coupled with the second waveguide; and amotion sensor coupled with the second modulator, wherein the imagesensor is configured to generate image data of an environment in whichthe apparatus is located; wherein the first modulator is configured tomodulate the light propagating in the first waveguide based on the imagedata; wherein the motion sensor is configured to generate motion data ofthe wearable device; wherein the second modulator is configured tomodulate the light propagating in the second waveguide based on themotion data; and wherein the second waveguide is configured to propagatethe light modulated by at least one of the first modulator or the secondmodulator towards the receiver device, to enable the receiver device toobtain at least one of the image data or the motion data and to enablethe wearable device to determine output content based on the at leastone of the image data or the motion data.
 2. The apparatus of claim 1,wherein the apparatus is a first apparatus of the wearable device; andwherein the light source and the receiver device are in a secondapparatus that is also part of the wearable device.
 3. The apparatus ofclaim 1, wherein: the first modulator and the second modulator arescheduled to modulate the light transmitted in the first waveguide atdifferent times based on a time-division multiple access (TDMA) scheme.4. The apparatus of claim 3, wherein the light is associated with asingle wavelength.
 5. The apparatus of claim 4, further comprising: afirst buffer coupled with the image sensor; and a second buffer coupledwith the motion sensor; wherein the first buffer is configured to storethe image data generated by the image sensor during a time when thefirst modulator is not scheduled to modulate the light propagating inthe first waveguide; and wherein the second buffer is configured tostore the motion data generated by the motion sensor during a time whenthe second modulator is not scheduled to modulate the light propagatingin the second waveguide.
 6. The apparatus of claim 1, wherein: the lightincludes a first component associated with a first wavelength and asecond component associated with a second wavelength; and the firstmodulator and the second modulator are configured to modulate,respectively, the first component based on the image data and the secondcomponent based on the motion data according to a wavelength divisionmultiple access (WDMA) scheme.
 7. The apparatus of claim 6, wherein thefirst modulator and the second modulator are configured to modulate,respectively, the first component and the second component atsubstantially identical time.
 8. The apparatus of claim 1, wherein thefirst modulator is configured to modulate an intensity of the lightpropagating in the first waveguide; and wherein the second modulator isconfigured to modulate an intensity of light propagating in the secondwaveguide.
 9. The apparatus of claim 8, wherein the first modulatorcomprises a first ring resonator, the first ring resonator beingassociated with a configurable first resonant frequency, the first ringresonator being capable of changing the intensity of the lightpropagating in the first waveguide based on a relationship between thefirst resonant frequency and a frequency of a component of the lightpropagating in the first waveguide; wherein the second modulatorcomprises a second ring resonator, the second ring resonator beingassociated with a configurable second resonant frequency, the secondring resonator being capable of changing the intensity of the lightpropagating in the second waveguide based on a relationship between thesecond resonant frequency and a frequency of a component of the lightpropagating in the second waveguide; wherein the first modulator isconfigured to modulate the first resonant frequency of the first ringresonator to modulate the intensity of the light propagating in thefirst waveguide; and wherein the second modulator is configured tomodulate the second resonant frequency of the second ring resonator tomodulate the intensity of the light propagating in the second waveguide.10. The apparatus of claim 9, wherein the first modulator includes afirst diode controllable to change the first resonant frequency of thefirst ring resonator by at least changing a free carrier concentrationwithin the first ring resonator; and wherein the second modulatorincludes a second diode controllable to change the second resonantfrequency of the second ring resonator by at least changing a freecarrier concentration within the second ring resonator.
 11. Theapparatus of claim 1, wherein: the first waveguide comprises a firstsilicon waveguide; and the second waveguide comprises a second siliconwaveguide.
 12. The apparatus of claim 11, wherein: the first siliconwaveguide is part of a first chip; the second silicon waveguide is partof a second chip; and the first silicon waveguide of the first chip iscoupled with the second silicon waveguide of the second chip via anoptical fiber.
 13. The apparatus of claim 12, further comprising: afirst grating coupler; and a second grating coupler, wherein the firstgrating coupler is coupled with the first silicon waveguide and with afirst end of the optical fiber to direct the light from the firstsilicon waveguide into the optical fiber; and wherein the second gratingcoupler is coupled with a second end of the optical fiber and with thesecond silicon waveguide to direct the light from the optical fiber intothe second silicon waveguide.
 14. The apparatus of claim 12, wherein:the first silicon waveguide and the first modulator forms a firstsilicon photonic die; the image sensor is part of a first sensor die;the first chip comprises the first sensor die and the first siliconphotonic die forming a first vertical stack structure; the secondsilicon waveguide and the second modulator forms a second siliconphotonic die; the motion sensor is part of a second sensor die; and thesecond chip comprises the second sensor die and the second siliconphotonic die forming a second vertical stack structure.
 15. Theapparatus of claim 1, wherein at least one of the image data or themotion data are defined according to an application layer protocolspecification of Mobile Industry Processor Interface (MIPI).
 16. Theapparatus of claim 1, further comprising a set of electrical signalpaths coupled with each of the image sensor and the motion sensor;wherein the set of electrical signal paths are configured to transmitcontrol signals and clock signals from a controller to each of the imagesensor and to the motion sensor.
 17. The apparatus of claim 1, whereinthe first waveguide and the second waveguide forms a shared physicalmedium over which one or more communication channels are formed, thephysical medium being shared between the image sensor and the motionsensor for transmission to the receiver device using the one or morecommunication channels.
 18. The apparatus of claim 1, wherein the motiondata comprise data for tracking a location of the wearable device. 19.The apparatus of claim 1, wherein the first modulator and the secondmodulator are configured to switch between a TDMA scheme and a WDMAscheme to modulate the light based on a mode of operation of apparatus.20. The apparatus of claim 19, wherein the first modulator and thesecond modulator are configured to modulate the light based on the TDMAscheme when the apparatus is in a low power mode and to modulate thelight based on the WDMA scheme when the apparatus is in a high powermode.
 21. The apparatus of claim 19, wherein the first modulator and thesecond modulator are configured to modulate the light based on the TDMAscheme when the apparatus in a static mode and to modulate the lightbased on the WDMA scheme when the apparatus is in a non-static mode. 22.The apparatus of claim 1, wherein the image sensor is a first imagesensor; wherein the apparatus further comprises: a third waveguide withthe first waveguide and a fourth waveguide coupled with the secondwaveguide to form the propagation path; a third modulator coupled withthe third waveguide; a fourth modulator coupled with the fourthwaveguide; a second image sensor coupled with the third modulator; and alocations sensor coupled with the fourth modulator; wherein the firstmodulator and the third modulator are configured to modulate the lightbased on a WDMA scheme; and wherein the second modulator and the fourthmodulator are configured to modulate the light based on a TDMA scheme.23. A method, comprising: transmitting light through a propagation pathcomprising a first waveguide of a wearable device and a second waveguideof the wearable device, the light being originated at a light source ofthe wearable device; modulating the light transmitted in the firstwaveguide based on image data of an environment in which the wearabledevice is located, the image data being generated by an image sensor ofthe wearable device; modulating the light transmitted in the secondwaveguide based on motion data of the wearable device generated by amotion sensor of the wearable device; and transmitting, via the secondwaveguide, the light modulated based on at least one of the image dataor the image data towards a receiver device of the wearable device toenable the wearable device to determine output content based on the atleast one of the image data or the motion data.
 24. The method of claim23, wherein modulating the light transmitted in the first waveguidecomprises modulating a first frequency component of the lighttransmitted in the first waveguide; and wherein modulating the lighttransmitted in the second waveguide comprises modulating the firstfrequency component of the light transmitted in the second waveguide.25. The method of claim 23, wherein modulating the light in the firstwaveguide comprises modulating a first frequency component of the lighttransmitted in the first waveguide; and wherein modulating the lighttransmitted in the second waveguide comprises modulating a secondfrequency component of the light transmitted in the second waveguide.